1. Field of the Invention
This invention generally relates to vehicular anti-theft system and device, and especially to vehicular anti-theft system and device, which can control start-up of an engine of a vehicle such as an automobile, and to engine control system and device having an anti-theft device.
2. Related Art
In the anti-theft device, various countermeasures have been developed to prevent vehicles from being stolen by manipulating an ignition key cylinder either with or without the use of a regular (valid) ignition key.
In this kind of anti-theft device, an electronic ignition key (hereinafter, called "ignition key"), which is unique to each vehicle, generally has a unique password code therein. An immobilizer device provided in the vehicle reads the password stored in the ignition key, and detects whether a start-up of an engine is due to a regular operation or not by collating the read password and a vehicular password code stored in the immobilizer device.
An engine control device, which controls the engine of the vehicle, detects whether the start-up of the engine is due to a regular operation (valid operation) or not by communicating with the immobilizer via a communication line. When the start-up of the engine is not detected to the regular operation, the immobilizer stops the engine.
Next, a communication procedure between the engine control device and the immobilizer will be explained.
(1) At first, when the engine control device starts up its operation by being supplied with a power from a battery, the engine control device sends a request signal for requesting a collation result of the password codes to the immobilizer.
(2) When the immobilizer receives the request signal sent from the engine control device in the procedure (1), the immobilizer sends a collation result signal, which indicates whether the password code in the ignition key accords with the password code in the vehicle, to the engine control device.
(3) After that, the engine control device receives the collation result signal sent from the immobilizer in the procedure (2). When the collation result signal is one that indicates an accord of the passwords, the immobilizer generates a random number by a predetermined method. Furthermore, the engine control device generates a transmission data by, for example, encoding the generated random number and then sends the transmission data to the immobilizer.
(4) When the immobilizer receives the transmission data sent from the engine control device in the procedure (3), the immobilizer processes the received transmission data with a predetermined process and then sends the processed transmission data to the engine control device as a response data.
(5) After that, the engine control device receives the response data sent from the immobilizer in the procedure (4), and extracts the random number from the response data by using a decoding process relative to the predetermined process in the procedure (4). The engine control device detects whether the extracted random number accords with the random number sent to the immobilizer in the procedure (3). When the random numbers accord each other, the engine control device detects that the start-up of the engine is due to the regular operation but not due to an unjust conduct, and then starts regular engine control. On the contrary, when the random numbers do not accord each other, or when the engine control device does not receive the response data from the immobilizer within a predetermined time although the engine control device has sent the transmission data in the procedure (3), the engine control device detects that the start-up of the engine is due to the unjust conduct, and then stops the engine.
Here, reasons to process the communication procedures (3)-(5) will be explained.
When the engine control device detects the operation of the start-up of the engine based on only the collation result signal sent from the immobilizer in the procedure (2), a person who intends to steal the vehicle may be able to start up the engine by, for example, the following manipulation. That is, the collation result signal being sent in a regular operation (the collation result signal indicating the accord between the password code of the ignition key and the password code of the vehicle) from the immobilizer to the engine control device is previously investigated by using this vehicle or another vehicle. In this case, when the investigated collation result signal is input to the communication line of the engine control device of this vehicle, the engine control device may start up the engine of this vehicle.
Therefore, by processing the procedures (3)-(5), the engine control device can confirm that the immobilizer correctly operates with no unjust conduct.
Especially, reasons, of which the engine control device generates the random number and further generates the transmission data to the immobilizer based on the random number, are that the engine control device changes the communication data being communicated between the engine control device and the immobilizer at random at every communication.
That is, if the communication data being communicated between the engine control device and the immobilizer are always the same, a person who intends to steal the vehicle may start up the engine by, for example, the following manipulation. That is, the communication data being communicated between the engine control device and the immobilizer is previously investigated by using this vehicle or another vehicle. In this case, when the investigated communication data is input to the communication line of the engine control device of this vehicle, the engine control device may start up the engine of this vehicle.
Therefore, by generating the random data and the transmission data to the immobilizer from the random data (furthermore, a detection data being communicated between the engine control device and the immobilizer to detect whether the start-up of the engine is due to the regular operation or not), the communication data being communicated between the engine control device and the immobilizer is changed at every communication. Therefore, a security performance against a theft of the vehicle can largely improve.
Here, such an engine control device constituting a vehicular anti-theft device generates the random number based on a counter value of a free running counter always operating in a microcomputer, or a time value of a clock separately built in itself. For example, there have been proposed an engine control devices in which a counter value of the free running counter is read at the time just before the engine control device sends the transmission data to the immobilizer so that the read counter value is used as the random number, and in which a time of the clock is read at the time just before the engine control device sends the transmission data to the immobilizer so that a data indicating the read time is used as the random number.
However, the above-described engine control device needs to detect whether it should start up the engine or not before starting the engine control after a power is supplied thereto from a battery. Therefore, in general, the engine control device generates the random number at a specific period (for example, a timing around 100 ms) which is just after starting the operation from an initial condition (reset condition) after a power is supplied thereto from the battery.
Therefore, in the case that the random number is generated based on the counter value of the free running counter, the count value of the free running counter is concentrated to the specific period. At a result, the random number to be generated is also concentrated to a specific range of value. Therefore, the transmission data which is sent from the engine control device to the immobilizer device, and the response data which is sent from the immobilizer to the engine control device in response to the transmission data are not changed at every communication. Hence, it may be difficult to have high security performance against the theft of the vehicle.
On the contrary, in the case the random number is generated based on the time of the clock, it may useful to generate the random number (furthermore, the communication data between the engine control device and the immobilizer) completely at random. However, because such the engine control device needs to have additional clock, which is not needed the other purpose, in the engine control device, a total mounting area and a total cost may increase. Furthermore, because it needs to supply a power from the battery to the engine control device all the time, a power consumption of the battery may increase.